"other considerations"

Reading the Sotomayor book, mention was made of a 1950s USSC ruling involving exclusion of Mexicans from juries in Texas that recognized Hispanics are protected by the 14A:

Throughout our history differences in race and color have defined easily identifiable groups which have at times required the aid of the courts in securing equal treatment under the laws. But community prejudices are not static, and from time to time other differences from the community norm may define other groups which need the same protection. Whether such a group exists within a community is a question of fact. When the existence of a distinct class is demonstrated, and it is further shown that the laws, as written or as applied, single out that class for different treatment not based on some reasonable classification, the guarantees of the Constitution have been violated. The Fourteenth Amendment is not directed solely against discrimination due to a 'two-class theory'—that is, based upon differences between 'white' and Negro.

This runs counter to people, down until today in things like same sex marriage, who say the 14A Equal Protection Clause -- the text aside -- only concerns itself with blacks. The application to "race" generally, which widely would include alienage and religious groups ("Arabs" and "Jews" originally considered as racial groups, e.g., and such was the case even into the 1980s)  is a fairly uncontroversial, at least now, application. 

But, "distinct class" rule is wider.  A half-century before that ruling:

Of course, if such discrimination were purely arbitrary, oppressive, or capricious, and made to depend upon differences of color, race, nativity, religious opinions, political affiliations, or other considerations having no possible connection with the duties of citizens as taxpayers, such exemption would be pure favoritism, and a denial of the equal protection of the laws to the less favored classes.

Note how "color" and "race" are set forth in a list, so it is not even that they deserve special concern.  But, even granting that, the "arbitrary" rule, the "no legitimate state interest" rule widely applied for over a century.  It helped when dealing with federal legislation, since without a federal equal protection provision, equal protection was often protected as a matter of due process. An "arbitrary" (discretion not based on legitimate reason) law was seen illegitimate, not an appropriate legislative practice. "Substantive due process" continues to be seen by some as an oxymoron, but various accounts show historical practice honored this rule as well.

The test as expressed, though this was in 1900 after all, sounds a bit easy to make -- "no possible" isn't that hard.  The courts had a low bar for reasonableness in that era even in the area now seen as fundamental rights. Meyer v. Nebraska, an important early precedent for privacy rights, e.g., noted in the 1920s:

The established doctrine is that this liberty may not be interfered with, under the guise of protecting the public interest, by legislative action which is arbitrary or without reasonable relation to some purpose within the competency of the State to effect. Determination by the legislature of what constitutes proper exercise of police power is not final or conclusive, but is subject to supervision by the courts.

The phrasing suggests the complexity of the rule -- something can have a "reason," but it might not be an appropriate purpose. For instance, it might interfere with parental decision-making over education without be justified by some "emergency" or other strong interest (citing an "emergency" as not being present suggests the test is not quite as weak as it sounds -- it might be thought that something much less would do the trick). 

The rules in certain ways are stronger and classes of scrutiny has some logic (race remains more clearly wrong than let's say occupation) but some basics stay the same.  Constitutional protections are not in place merely for the central reason behind their births. It bears noting that even there the 14A was originally also there to protect non-blacks, such as Republicans and others felt to have been mistreated in antebellum times and later. Anyway, the language is general, was intended to be so, and clearly is appropriately so today.  The need being a question of fact.

The particulars changing from "time to time."